High Impedance Differential protection
High Impedance Differential protection
(OP)
Our client uses High impedance circulating current principle for Restricted Earth fault protection and for Busbar protection.
Of late there is discussion with some section of engineers saying we should change with times and low impedance type protection is the order of the day and entire world is after all changing and so on.
As protection engineer, I am conversant with the merits/demerits of high impedance based protection and personally hold the view that unless driven by need, there is no point in changing the protection philosophy just because others are doing and such reasons.
I am also aware low impedance differential protection from ABB (RADSS) was available since 1980s (or even before.
I would like to know the views of the learned members of this forum.
I would also like to see if some one has statistical data as to how many utilities of the world still continue to use the High impedance principle based differential protection.
I know CIGRE collects such data and I am not sure they have done it on this particular issue.
Thanks in anticipation.
Of late there is discussion with some section of engineers saying we should change with times and low impedance type protection is the order of the day and entire world is after all changing and so on.
As protection engineer, I am conversant with the merits/demerits of high impedance based protection and personally hold the view that unless driven by need, there is no point in changing the protection philosophy just because others are doing and such reasons.
I am also aware low impedance differential protection from ABB (RADSS) was available since 1980s (or even before.
I would like to know the views of the learned members of this forum.
I would also like to see if some one has statistical data as to how many utilities of the world still continue to use the High impedance principle based differential protection.
I know CIGRE collects such data and I am not sure they have done it on this particular issue.
Thanks in anticipation.






RE: High Impedance Differential protection
RE: High Impedance Differential protection
Regards
Marmite
RE: High Impedance Differential protection
From the merits and demerits and cosidering the economic sense vis a vis sensitivity then I don't see why you can decide suddenly to overhaul the scheme.
Unless the relays have deterorited then I think you should maintain the relays. We still use PBOs, TJMs and FACs and they serve well the purposes.....
RE: High Impedance Differential protection
Raghun is very, very intresting Q.
About REF HI, Marmite thanks a lot for the document.
Many countries/utilities request REF HI ( I see from time to time projects for ME, India and others).
On other hand, I see utilities at retrofir time disconnect REF HI and used REF LI only, but for the big AT still used REF HI.
BBP, as Rakan said, for the 400kV one and half CB configuration used HI BBP, but as combination of LI and HI
BBP for redandancy.
Lot of new projects in ME and Eroupean contries used only LI BBP, but for the redundancy used two options:
1. two LI BBP or one LI BBP and additional separated LI BFP
is connected to different CT's.
Best Regards.
Slava
RE: High Impedance Differential protection
I would like add some intresting document about 87T ( diff )
protection. isn't exactly about OP, but..
http
Additional about HI BFP,
RADSS is great protection, but "problem" isn't RADSS, are class Px CT's( we need use same CT ratio on all bays for the BBP HI) and BB replika EM relays. Before 2 years flashover on this relay was reason for serious fault in our area. For RADSS we always need RAICA ( BFP), as separate relay and many times connected to the separated CT core.
I don't say about end-fault protection. Optionality for the bay protective functionality in the BBP.
Economical reason, less wiring, more flexibility is reason for used modern LI BBP instaed perfect HI BBP.
Just my pinion.
Best Regards.
Slava
RE: High Impedance Differential protection
Marmite, Thanks for the informative paper on REF protection.
But, I am still looking for some idea as to how many utilities in the world still continue to specify High impedance type REF/Busbar protection!
RE: High Impedance Differential protection
Schweitzer uses a directional element in their SEL-387 for transformer REF protecdtion.
RE: High Impedance Differential protection
AREVA also sells MCAG and MFAC models for High impedance differential protection. They too seem to be doing well.
RE: High Impedance Differential protection
Maybe possible ask your local ABB, Areva, GE, Siemens for the reference list.
Best Regards.
Slava